I cannot tell how to export from server, as that is your account. See if you can export as CSV format, as that is fairly common and can readily be imported. So, the first task is for you to see what mail.com offers.

Thanks David. I know how to do that. I just thought that Thunderbird would automatically import this and keep it updated. I have 4 devices that access my emails and that I respond from. On my work computer I thought is was keeping this updated? Maybe? or no? Not all devices are using Thunderbird.

Well, Thunderbird was developed to serve one user. If you share addresses with other computers, I suggest setting up an online addressbook, such as with Gmail. Thunderbird can easily use that and it can be shared with any number of computers.

Ok I will look into that Thanks for your help David

It is one user, just me, but I have 4 devices that I use, work computer, phone, tablet, and now this personal computer. I will look at my work computer on Monday and probably just comp that contact list (csv) to this computer.

Tip: setting up CSV can be difficult, mirroring whatever you download to match the layout of Thunderbird. These steps usually work - create at least one address in the thunderbird addressbook - highlight the book, click the three dots to the right and export the CSV. - use this as a template for whatever you export from your work PC. - open in spreadsheet software to see exact layout of first row. That is the ticket - use that first row as a guideline in rearranging your work CSV so it is a perfect match - then the import should go smoothly.